Vertical-axis wind turbine

[00002] This invention relates generally to wind turbines and, more particularly, to a vertical-axis wind turbine that arranges stationary and rotor blades so as to harness and utilize a properly directed airflow while restricting an improperly directed airflow and eliminating inefficient internal airflow restrictions.

[00003] Harnessing wind energy and converting it to mechanical or electric energy has long been considered to be a promising source of energy generation. In fact, many devices have been proposed for harnessing wind for this purpose. Wind turbines are generally placed into two categories: horizontal-axis turbines (propeller windmills) which operate directly into the wind and turn about a horizontal axis and vertical-axis turbines which harness columns of air to turn rotor blades rotating about a vertical axis. Although each type of wind turbine has advantages and disadvantages, existing devices do not provide the proper arrangement of stationary and rotational blades and internal structures that make converting wind energy to electric energy feasible.

[00004] Therefore, it is desirable to have a vertical-axis wind turbine that tangentially directs an airflow to a rotor assembly so that an airflow that will provide sail-type propulsive force is unrestricted and an airflow that will cause drag is blocked. Further, it is desirable to have a vertical-axis wind turbine having no center vertical shaft so that an airflow is allowed to flow unobstructed through the center of a rotor assembly. It is also desirable to have a wind turbine in which the rotor blades include an angular configuration that optimally balances sail propulsion and lift effects.

[00005] A vertical-axis wind turbine according to the present invention includes a rotor assembly having top and bottom plates pivotally connected to upper and lower bearing hubs for rotation about an imaginary vertical axis extending between the bearing hubs. The bearing hubs themselves are positioned within the turbine housing. The rotor assembly includes a plurality of rotor blades, each rotor blade having a generally annular configuration and being positioned so as not to contact any other rotor blade. Each rotor blade includes one vertical edge adjacent to the radial edge of the top and bottom plates of the rotor assembly and a second vertical edge extending toward the imaginary vertical axis. However, each rotor blade stops short of the axis such that the rotor assembly defines an open center space through which an airflow may pass without obstruction or resistance.

[00006] The wind turbine further includes a plurality of stationary stator blades arranged about the circumference of the rotor assembly, each stator blade being positioned in a tangential relationship relative to the rotor assembly. This configuration only allows air to enter the rotor assembly that will impact the propulsion side of respective rotor blades like a sail or to be diverted to such a rotor blade. Air flowing in a direction that would cause drag on the rotor blades is blocked. Of course, air flowing in the proper direction will sometimes flow to the backside of a rotor blade due to the constant rotation of the rotor assembly; this is acceptable as such an airflow provides a propulsive lift effect. Therefore, the rotor assembly as a whole may provide both sail and lift types of propulsion.

[00007] Therefore, a general object of this invention is to provide a vertical-axis wind turbine that includes a rotator assembly having no center shaft such that an airflow may pass therethrough without obstruction or resistance.

[00008] Another object of this invention is to have a wind turbine, as aforesaid, having a plurality of stationary stator blades arranged circumferentially about the rotor assembly with each stator blade being positioned tangentially relative to the rotor assembly for permitting or restricting airflow from certain directions.

[00009] Still another object of this invention is to have a wind turbine, as aforesaid, in which each of a plurality of rotor blades includes an airfoil configuration which may act as an airfoil or sail depending on an angle of an incoming airflow.

[00010] Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, embodiments of this invention.

[00025] A vertical-axis wind turbine according to the present invention will now be described in detail with reference to FIGS. 1 through 14 of the accompanying drawings.

[00026] A vertical-axis wind turbine 10 according to one embodiment of the present invention is shown in FIGS. 1 through 10 and includes a housing having a plurality of spaced apart separator plates 12, the separator plates each having a circular configuration and being arranged in a parallel, stacked configuration (FIGS. 1-3). It is understood that the separator plates 12 may have other configurations, such as octagonal (FIG. 13), square (FIG. 14), or other suitable planar configurations. The separator plates 12 act as a ceiling and base to multiple vertically adjacent rotor assemblies positioned therebetween, as to be described in more detail below. It should also be appreciated that while the wind turbine 10 preferably includes multiple rotor assemblies (FIGS. 1-3), a single stage design would also work (FIG. 7). In a single stage design, the separator plates serve as a ceiling and base.

[00027] The wind turbine 10 includes a rotor assembly 14 positioned between adjacent separator plates 12 (FIG. 2). Each rotor assembly 14 includes spaced apart top 16 and bottom 18 walls, the top 16 and bottom 18 walls having circular configurations. Outer surfaces of each top 16 and bottom 18 wall are rotatably coupled to respective separator plates 12 with upper 20 and lower 21 bearing hubs (FIGS. 2, 4, 9). These hubs enable a rotor assembly 14 to rotate freely about an imaginary vertical axis extending between corresponding hubs as an airflow passes therethrough, as to be described in more detail below. The upper 20 and lower 21 hubs will hereinafter be referred to generically with reference numeral 20.

[00028] Preferably, a diameter of each separator plate 12 is at least three times larger than a diameter of a rotor assembly 14. The ratio of the housing to the rotor assembly is important in that the housing configuration (separator plates) accelerate the air so as to create a higher wind speed before the air enters the rotor assembly 14. Therefore, the larger the housing, the greater the increase in wind speed.

[00029] Each rotor assembly 14 includes a plurality of spaced apart rotor blades 24 situated adjacent the radial edges of the top 16 and bottom 18 walls and extending perpendicularly therebetween (FIG. 6). Having eight rotor blades has been determined to provide optimal performance although having between 6 and 10 blades would be adequate. Further, each rotor blade 24 includes a first vertical edge 26 extending between radial edges of respective top 16 and bottom 18 walls. Each rotor blade 24 further includes a second vertical edge 28 parallel to the first vertical edge 26 but spaced inwardly toward the respective imaginary vertical axis of the respective rotor assembly 14. Each rotor blade 24 only extend partially between the radial edges of the top 16 and bottom 18 walls and the respective imaginary vertical axis such that the respective rotor assembly 14 maintains an open center area. The open center area is primarily characterized, of course, by its lack of a center shaft.

[00030] In addition, each rotor blade 24 includes an airfoil configuration with a curved portion adjacent the radial edacs 16, 18 of the rotor assembly and a generally linear portion extending inwardly therefrom in a direction toward the imaginary vertical axis wherein the curved portion curves away from the generally linear portion toward an outer circumference of the rotor assembly so as to act as an airfoil under appropriate airflow conditions. More particularly, an airfoil generates lift when the chord line of the airfoil is oriented parallel to the wind. In other words, when an incoming airflow passes over the back side (outwardly curved portion) of an airfoil, low pressure is created which contributes to propulsion. On the other hand, when an incoming airflow strikes the front side (inwardly curved portion) substantially directly, the rotor blade arts as a sail which directly contributes to propulsion.

[00031] To generate further lift, each rotor blade 24 is angularly offset from an imaginary radial line extending between the imaginary vertical axis and the respective rotor blade. A large angular offset (e.g. 40°) reduces sail propulsion potential but increases lift potential, and vice versa (e.g. 0°). Preferably, each rotor blade 24 is angularly offset 20° from this imaginary radial line so as to optimize the lift and sail propulsion characteristics of the rotor assembly although other angular offsets are possible.

[00032] The wind turbine 10 further includes a plurality of stationary stator blades 30 arranged circumferentially and spaced apart about the rotor assembly 14 (FIG. 6). Each stator blade is upstanding between adjacent separator plates 12 (FIGS. 1 and 2). Each stator blade 30 presents a linear configuration and is positioned tangentially to the radial edge of a rotor assembly 14. This configuration and arrangement allows an airflow to flow directly and unrestricted to a propulsion rotor blade while restricting an airflow that would cause drag on the rotor blade (FIG. 6). It should be appreciated that even when an airflow does not directly impact the first rotor blade toward which it is directed (i.e. there is no “sail” propulsion), the airflow may pass in part along the backside of the rotor blade to promote lift propulsion and then flow directly through the open center area and impact rotor blades along the far side of the rotor assembly for sail type propulsion. At the same time, the stator blades 30 block airflow moving in a direction that would cause drag on the rotor blades 24. By directing a large amount of air into a small opening of a rotor assembly, the air velocity is also increased which enhances propulsion.

[00033] Various configurations of the separator plates 12 may be utilized, even within the multi-stage housing shown in FIG. 1. An inwardly sloped separator plate such as the convex lowermost plate shown in FIGS. 1, 2, and 5 allows for the collection of a large amount of air and then compresses/speeds it as it flows into the respective rotor assembly. Obviously, the stator blades 30′ attached thereto will have a variable height as a result (FIG. 5). The convex configuration is also advantageous in that an electrical generator 40 may be positioned therein and coupled to the rotating bearing hubs 20. The parallel configuration of the intermediate and uppermost separator plates is advantageous in that they are simple to manufacture and conducive to stacking.

[00034] As previously mentioned, a generator 40 capable of converting rotational mechanical energy to electric energy is coupled to the lowermost bearing hub (FIGS. 2 and 3). Each hub includes a shaft 22 that extends through a respective separator plate 12 and connects to the next adjacent hub such that adjacent rotor assemblies are linked together. Therefore, the mechanical energy of all the rotor assemblies may be harnessed by the generator 40.

[00035] A measurement module 42 may be electrically connected to the generator 40 for calculating the amount of electrical power generated by the generator 40 (FIGS. 2 and 3). Such a measurement is calculated as the mathematical product of voltage and current produced by the generator 40. Alternatively, the amount of mechanical power generated by the rotor assemblies may be calculated using conventional load cells or strain gauges (not shown) which produce an electronic signal proportionate to the force on the respective sensor. A pulley system whereby the rotor assemblies lift a weight would also be suitable, the power calculation revealing the number of watts produced. Other suitable measurement options would be a digital handheld tachometer or digital bicycle speedometer to measure rpm's or speed, respectively.

[00036] Although the uppermost rotor assembly is sandwiched between parallel separator plates 12, a roof 50 having a dome-shaped configuration may be fixedly attached to the uppermost separator plate for deflecting weather elements away from the housing and rotor assemblies (FIG. 2).

[00037] In operation, an airflow is naturally harnessed between adjacent separator plates 12 and between respective stator blades 30. This airflow is naturally compressed by the configuration of the separator plates 12 and placement of the stator blades 30 such that the velocity of the airflow is increased before entering a respective rotor assembly 14. The tangential placement of stator blades 30 also blocks an airflow that is flowing in such a direction as would cause resistance against the rotating rotor blades 24. The tangential placement of the stator blades 30 will either direct the airflow into direct contact with the front face of a rotor blade 24 and cause sail-type propulsion or will be diverted around the rotor blade 24 and cause lift-type propulsion, depending upon the exact position of the rotor blade 24 at the time. If the airflow is diverted, it flows without obstruction through the rotor assembly 14 until it contacts a far-side rotor blade for sail-type propulsion. The center of the rotor assembly 14 does not include a center shaft; therefore, efficient conversion of airflow energy to propulsive rotational energy is not hampered or decreased by unnecessary resistance. The configuration of each rotor blade 24 is like an airfoil and is angularly diverted to optimize both sail-type and lift-type propulsive effects. The rotor assemblies are connected to the electric generator 40 for converting airflow energy to electric energy.

[00038] Another embodiment of a rotor assembly 60 for use in a vertical-axis wind turbine according to the present invention is shown in FIG. 11 and includes a construction that is substantially similar to the rotor assembly construction described above except as noted below. In this rotor assembly 60, a center shaft 62 extends between upper 64 and lower 66 bearings and a plurality of spokes 68 extend radially from the center shaft 62. Radial ends of the spokes 68 are fixedly attached to outer vertical edges 70 of respective rotor blades 72. The use of a center shaft 62 makes manufacture of the rotor assembly 60 more cost-effective and simple in that top and bottom walls to support the rotor blades are unnecessary.

[00039] Another embodiment of a rotor assembly 80 is shown in FIG. 12 that includes a construction substantially similar to that of FIG. 11 except that radial ends of the spokes 68 are fixedly attached to inner vertical edges 82 of respective rotor blades 72. This rotor assembly 80 is shown in use with a housing having a square-shaped separator plate in FIG. 14.

[00040] It is understood that while certain forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims and allowable functional equivalents thereof.